Thread: Whats the difference between

Another very important reason for use of multi strand is that apart from flexing....e.g. moving and snaking weding leads around on a job....is that multi-strand is LESS RIGID and thus much, much [for most practical purposes, immune from] less likely to suffer embrittlement due to vibration from a wide range of frequencies such as vehicle vibration [in case you drive your Landy on roads of lesser quality than billiard tables surfaces!] and natural harmonics from your diesel [even dual mass flywheel TD5's] or V8 and all the other rotating masses in your car from tyres, brakes, gears to a;ternators or even worse, reciprocating masses such as pistons [for one!], non-rotary pumps e.g. A/C compressors,.....the list goes on.....

Embrittlement will eventually lead to ever increasing rise in microscopic fracturing and failure due to stress fracture......as well as that is the concommitant ever increasing resistance due to same micro fracturing.

Originally Posted by byron

Another reason for use of multi strand is that apart from flexing....e.g. moving and snaking weding leads around on a job....is that multi-strand is LESS RIGID and thus much, much [for most practical purposes, immune from] less likely to suffer embrittlement due to vibration from a wide range of frequencies such as vehicle vibration [in case you drive your Landy on roads of lesser quality than billiard tables surfaces!] and natural harmonics from your diesel [even dual mass flywheel TD5's] or V8 and all the other rotating masses in your car from tyres, brakes, gears to a;ternators or even worse, reciprocating masses such as non-rotary pumps e.g. A/C compressors.....the list goes on.....

Embrittlement will eventually lead to ever increasing rise in microscopic fracturing and failure due to stress fracture......as well as that is the concommitant ever increasing resistance due to same micro fracturing.

I agree entirely with this - except for "Another reason for use of multi strand is that apart from flexing..." because everything after this is talking about why flexing is important even when the need for it is not obvious rather than a different factor. All vehicles have a lot of vibration, for the reasons you mention, and the flexing of wires due to this vibration needs to cause a level of strain within the metal small enough to avoid fatigue - and this is done by using strands small enough in diameter that the bending causes sufficiently low strain - in other words, the cable of adequate cross section area is sufficiently flexible.
John

Originally Posted by p38arover

The number of strands is only important for flexibility in DC applications. We've already been through the surface effect misconceptions in earlier posts.

Where I used to work, our 3000Ah batteries were connected with solid copper buss-bar about 100mm x 10mm in section.

Ron

When I briefly worked at Metal Manufactures Ltd. makers of the "Kembla" range of tube, strip, conductor, etc., they had a product called "high conductivity oxygen free copper". Not being an electrical type I never bothered going into the make-up or uses of this. I remember it being sold for bus bar and once, a fairly large order for 30mm heavy wall tube for use at a sub-station. The guy from the electric authority said the reason for tubular bus bar was for cooling purposes. Can anyone enlighten?

Originally Posted by Brian Hjelm

When I briefly worked at Metal Manufactures Ltd. makers of the "Kembla" range of tube, strip, conductor, etc., they had a product called "high conductivity oxygen free copper". Not being an electrical type I never bothered going into the make-up or uses of this. I remember it being sold for bus bar and once, a fairly large order for 30mm heavy wall tube for use at a sub-station. The guy from the electric authority said the reason for tubular bus bar was for cooling purposes. Can anyone enlighten?

The last few tenths of a percentage of purity in copper makes a significant difference to the conductivity, so when the application is critical, it is worth paying extra for the purer copper where there is no room for the extra cross section area.

In a very high current situation as air cooling depends on surface area and when you go to large cross-section area to reduce heating the cooling becomes inadequate because the surface area in contact with the air only increases as the diameter whereas the cross section area increases as the square of the diameter. The solution is to go to water cooling and run liquid through the middle of the bus bar. If you use distilled water it is an insulator, or more commonly you can use another non conducting fluid, typically an oil going to a radiator.
John

Originally Posted by byron

Yeah, so every [say] 12mm lenght of bar had 2640 mm2 of surface area!!!!!!! .......thus plenty of surface area!!!!!!!

Byron, you're stuck on this idea of surface area being important for DC. It ain't. It's cross-sectional area. Skin effect plays no part in conductivity with DC current.

Ron

Originally Posted by JDNSW

The last few tenths of a percentage of purity in copper makes a significant difference to the conductivity, so when the application is critical, it is worth paying extra for the purer copper where there is no room for the extra cross section area.

In a very high current situation as air cooling depends on surface area and when you go to large cross-section area to reduce heating the cooling becomes inadequate because the surface area in contact with the air only increases as the diameter whereas the cross section area increases as the square of the diameter. The solution is to go to water cooling and run liquid through the middle of the bus bar. If you use distilled water it is an insulator, or more commonly you can use another non conducting fluid, typically an oil going to a radiator.
John

John, I recall they used fans to blow cooling air through banks of these tubes, which had a wall thickness similar to screwing grade brass tube. The station was in coastal central Qld. and had to do with supply to coal mines. It was a good order, nice commission and plenty brownie points with head office.

Originally Posted by p38arover

Byron, you're stuck on this idea of surface area being important for DC. It ain't. It's cross-sectional area. Skin effect plays no part in conductivity with DC current.

Ron

but doesn't everyone know that electricity is smoke. if you let the smoke escape from an appliance, it never works again.

Originally Posted by Brian Hjelm

but doesn't everyone know that electricity is smoke. if you let the smoke escape from an appliance, it never works again.

You've answered your own question about the copper tubing. The tubing contains the smoke.

Ron